It is known that certain halogen substituted hydrocarbon monomers notably vinyl chloride have toxic properties. Naturally such monomers are handled with care. However, after polymerization of the monomer, the solid relatively inert plastic materials into which the monomer has been converted are considered safe, and concern over toxicity is virtually at an end. However, safety is relative. Possible presence of significant monomer residue in the plastic material may create a hazard due to long term exposure to the plastic material by workers therewith, even perhaps to consumers in the event the plastic material is a food stuff packaging material.
In this respect vinyl chloride may be particularly dangerous, since contact therewith might be one cause of liver cancer. Moreover, when a vinyl chloride monomer residue is present in the polymer e.g. in copolymer pellets or articles, detectable quantities of vinyl chloride and/or perhaps lower polymers of the vinyl chloride can be leached out of the pellet or article.
The concern which exists is, therefore, whether the content of residual halohydrocarbon monomer, principally of vinyl chloride, in polymer articles is high enough so that monomer and/or lower polymer components will migrate from a packaging material into food product contents therein.
Certainly, manufacturers of the polymer and of foodstuff packaging material made therefrom employ polymerization techniques that are adapted to minimize the monomer content in the polymer materials. However, despite their best efforts to provide monomerfree polymer pellets and best efforts to avoid degradation of the polymer during the package forming operations, a measurable residual monomer content almost always can be found in packaging materials made from polymers of halogenated hydrocarbon monomers and in the PVC pellets. Examples of such monomers are vinyl chloride, vinylidene chloride and chloroprene.